Figure 3

Assessment of damage and health in the facet joint’s cartilage, bone, and articular chondrocytes at 21 days post-injection. (a) Low and high magnification images of bone and cartilage staining with Safranin O/Fast Green reveals no significant difference in Mankin score (Wilcoxon test; p = 0.444); a mild decrease in cartilage staining and slight fibrillation is observed in some collagenase-injected joints. Similar to the Mankin score, neither joint space width (two-tailed t-test; p = 0.841) nor cartilage width (two-tailed t-test; p = 0.111) change after intra-articular collagenase (6 joints) compared to intra-articular vehicle (3 joints). (b) Images show chondrocytes in the articular cartilage immunolabeled with HIF-1α where black arrowheads indicate positive HIF-1α labeling. For each image, HIF-1α is quantified in regions that are four times larger than those shown in b; zoomed images are shown here to better visualize chondrocyte labeling. Chondrocytes exhibit a similar pattern of positive labeling regardless of group (collagenase n = 6; vehicle n = 3) that is not different (two-tailed t-test; p = 0.423). An image of the no primary, negative control for the HIF-1α label is also shown. Box-and-whisker plots show horizontal lines representing the first (lower) quartile, median, and third (upper) quartile of the data. Whiskers represent the minimum and maximum of the data set. Data points for individual joints are superimposed on boxplots and show the mean value from 6–8 images/rat for the Mankin score, 3–4 images/rat for the joint space and cartilage width measurements, and 5 images/rat for the HIF-1α labeling.